I won't mention the parties involved but basically one of our Exchange servers containing certain Public Folders was being re-sized hence an outage. Sadly our provider could not tell me who would be impacted!

Therefore should the CMDB contain users, mailbox location, public folder usage, etc? I hope you see where I'm getting to?

THe CMDB or any data base or any reference tool should not be used in place of the due diligence people should do

If I was running a project like that, I would look at EVERYTHING that could possibly be impacted by it as part of the risk assessment and classification of the risk potentials_________________John Hardesty
ITSM Manager's Certificate (Red Badge)

As maintenance is one of the major issues to consider, it makes sense to only consider including the data that can be easily maintained up to date and for which the maintenance overhead brings visible added value.

I can see the value of knowing which users are impacted by an outage. Currently in our company, when an outage occurs (planned or unplanned) ther service desk sends an email to the entire community notifying them of the outage. This leads to people being spammed and then ignoring the email when it is applicable to them. Our solution was to include the users associated with a particular service such that when there is an outage, we can target the outage email notification to only those impacted by the outage.

So, in our case, we do keep the users of services in our integrated CMDB. The actual userids are stored in groups in LDAP (MS Active Directory) and the groups associated with the services are in the cmdb